The leak detection tests of oil pipe line were carried out in Nu county Shandong province

using oil tracer of iodo-benzene (C

6

H

5

131

I) labeled by

131

I. C

6

H

5

131

I was obtained through iodination of diazotized aniline. Because of the diazo-compound is unstable

thus the iodo-benzene must be prepared in site. Apparatus for semi-automic and remote operation was designed. More than 300 mCi of C

6

H

5

131

I were prepared successfully and mixed with ten tons of petroleum

for leak detection of oil pipe line. It was demonstrated that the test was safe and reliable.